Process for producing alternating twist



Dec. 10,1968 A; WELBERS 3,415,048

PROCESS FOR PRODUCING AL-TERNATING TWIST I Filed March 28, 1966 2 Sheets-Sheetl Fig. 1

Dec. 10, 1968 A. WELBERS PROCESS FOR PRODUCING ALTERNATING TWIST Filed March 28, 1966 2 Shets-Sheet z I NVE NTOR A N TON WELBERS United States Patent 3,415,048 PROCESS FOR PRODUgING ALTERNATING TWI T Anton Welhers, Wildtal, near Freibnrg im Breisgau, Germany, assignor to Deutsche Rhodiaceta A.G., Freiburg im Breisgau, Germany Filed Mar. 28, 1966, Ser. No. 540,556 Claims priority, application Ggrmany, Apr. 7, 1965,

1s (Ilaims. in. 57-44 ABSTRACT OF THE DISCLOSURE aXn in which a is the length of the longer segment, n is the number of turns of the twister in a unit of time and v is the speed of the thread. The length of the thread segment is varied by the use of two twist barriers, of which the one which is closer to the twister, operates intermittently. It is also possible to have a single twist barrier which moves back and forth.

This invention relates to textile processing and more specifically, to the twisting of filaments and fibers.

In the case of fibers, they necessarily undergo a twisting step, as part of the spinning process. Here the fibers are drawn and then twisted, that is, the component fibers tend to take on a spiral arrangement, which serves to hold them together, shortens the yarn and increases the weight per unit length. Finally the spun yarn is wound onto a package. The spun yarn is a more or less compact group of fibers of suflicient strength to be utilized for the preparation of textiles.

Also in the case of filaments, twisting is necessary to increase the coherence and strength, especially in the transverse direction, to prevent their splitting off during the subsequent steps, usually weaving, and in general to improve the serviceability and durability of the finished products.

The amount of twisting required varies in each case. Filaments require less twisting than fibers. Fine yarns require more twisting than coarse yarns.

The direction of twist at each stage of manufacture is indicated by the use of the letters S or Z in accordance with the following convention:

A simple yarn has S-twist if, when it is held in the vertical position, the fibers inclined to the axis of the yarn, conform in direction of slope to the central portion of the letter S. Similarly, the yarn has Z-twist if the fibers inclined to the axis of the yarn, conform in direction of slope to the central portion of the letter Z.

Some attempts have been made to conduct the twisting of filaments continuously, as part of the spinning process, by passing the threads which emerge from the spinneret, onto a centrifugal spindle or onto a ring spindle. These processes have the disadvantage that it is necessary to interrupt or frequently slow down the operation because of the low capacity of the spindles, so that continuous surveillance is required and the processes cannot be 3,415,M8 Patented Dec. 10, 1968 conducted on a continuous scale. Further, the package emerging from the centrifugal or ring spindle frequently requires further processing, which makes it even more difficult to run the process continuously.

The recent process of imparting to the threads an alternating twist constitutes a substantial improvement, because it increases the strength of the filaments and allows a substantial reduction in cost. Essentially this process consists of imparting an S-twist to the thread, followed by a Z-twist or vice versa. The change in the direction of the twist may occur at regular or irregular intervals. Here the twists in one direction compensate the twists in the opposite direction, and the twist is called false-twist, because it alternates the twists in one direction with twists in the opposite direction, so that the overall elfect is as if the number of twists were equal to zero.

The most common method of producing the alternating twist is to apply twisting, alternately, at the left and at the right of the threads, with a twisting device, for instance, a twisting tube. Some success has also been claimed by application of air jets, which are allowed to blow alternately, from the right and from the left, tangentially to the filaments.

In spite of some improvement, the foregoing processes are not economical, because they cannot be conducted continuously after the spinning operation, and require changing the direction of the twisting device, at intervals.

The object of the present invention is to provide a process for achieving very efiicient twisting of filaments and threads, which may be conducted continuously, after the spinning step.

Another object is to provide a process which imparts an alternating twist to the threads and filaments in a very simple and inexpensive manner.

Still another object is to provide the apparatus for carrying out the process of this invention.

The crux of this invention resides in the finding that it is possible to achieve good alternating twist, by alternately increasing and decreasing the length of the thread segment in the path of travel before it reaches the twisting device, for instance a twisting tube. It is an essential feature of the invention that the supply package from which the thread is fed, for instance a dofiing, and the twisting tube operate at constant speed and that the twisting tube operates always in the same direction. By application of this simple device, alternately increasing and decreasing the length of the thread segment before the twisting tube, the overall effect is the same as the alternating twist, because a substantial number of twists accumulates in the shorter segment, before the twisting tube, and the twists are transferred to the last segment of the thread after the site of the twisting tube, with the opposite direction. In this manner, an alternating twist is produced, without the conventional device of changing the direction of the twisting tube. In accordance with this invention, the change of the length segment mentioned above, before the twisting tube, may be conducted gradually or abruptly.

The invention will now be described in detail by reference to the accompanying drawing, in which FIG. 1 is a schematic representation of the apparatus used for conducting the process of this invention, and FIG. 2 is a plot of the Z and S twists alternately produced by application of the process to a specific thread.

By reference to FIG. 1, the thread is fed from the supply package 5, for instance a doffing, along the path as shown, to the device 4, for instance a bobbin, where it is Wound. Guide means 7 and 8 are interposed along the path, to keep the thread in the desired location.

Numerals 1 and 2 designate two twist barriers which are set along the path of the thread, before the twisting device, shown at 3, for instance a twisting tube, such as a false twist tube or a fluid jet. The twisting tube always operates in the same direction and at constant speed throughout. The length of the thread segments between the two twist barriers 1 and 2, between twist barrier 1 and twisting tube 3, between twist barrier 2 and twisting tube 3, between the twisting tube 3 and bobbin 4, are essential features of the invention and must be predetermined in relationship to the speed of the twisting tube 3, the rate of flow of the thread from the dofiing and the rate of operation of twist barrier 2 which operates intermittently, in order to achieve the alternating twist, in accordance with this invention.

According to one embodiment of the invention (not shown in FIG. 1) it is not necessary to use two yarn twist barriers, but the yarn twist barrier 1 may move back and forth from position 1 to position 2.

In the first step of the process, the thread emerging from the doffing at a constant rate, is held by twist barrier 1 and twisted by the twisting tube 3. The number of turns in the segment 1-3 is controlled by the formula in which a is the length of the segment between twist barrier 1 and the twisting tube, It is the number of turns of the twisting tube 3 in a unit of time and v is the speed of the thread.

In a second step of the process, the yarn twist barrier 1 is moved from position 1 to position 2, thus shortening the distance of the segment 1-3. Of course, if two yarn twist barriers are used, yarn twist barrier 2, which is nearer the twisting device 3, than twist barrier 1, and which operates intermittently, is allowed to operate. Numeral 6 designates a cam mechanism for intermittently engaging twist barrier 2. It should be understood, however, that any mechanism, for instance, a mechanical or an electrical device, may be used to engage twist barrier 2 intermittently. During this second step, the twists accumulate from the longer segment 1-3 to the shorter segment 2-3.

In a third step, the thread segment 2-3 is allowed to extend to the original segment 1-3 by interrupting the operation of yarn twist barrier 2 or if only one yarn twist barrier is used, by moving the yarn brake back to position 1.

A cerain number of twists is transferred to the segment 3-4 after the number of twists determined by the formula is reached. If thread of Z-twist is fed from the doffing 5, and if the twisting tube 3 imparts an S-twist to the thread in the segment 1-3, the twists in segment 3-4 are in the direction opposite to that imparted by the twisting tube, that is, in the same direction as that of the thread before reaching twist barrier 1.

In the third step, the S-twists of segments 2-3 are transferred to the segment 3-4, meet the Z-twists of the latter segment, so that a compensating effect results. Since the number of the S-twists is greater than the number of the Z-twists, in segment 3-4, some S-twists are transferred to the thread which is being wound on the bobbin. By continuously repeating the process, an alternating twist is imparted to the thread, which is being wound, without at any time changing the direction of twisting tube 3.

Manifestly, in accordance with this invention, the height and interval of the twists depend on the speed of the twisting tube 3, the rate of feed from doffing 5, and the relative lengths of segments 1-3, 2-3, 2-4 and 3-4, and may be varied according to the nature of the threads involved and the intended ultimate use of the thread.

By plotting the Z-twists and S-twists, imparted to the thread which is wound onto the bobbin, a curve is obtained. In actual operation, because of the time lag in engaging and disengaging twist barrier 2, and in transferring the twists from segment 2-3 to segment 3-4, a flattening of the curve results.

For the purpose of further illustrating the invention the following example is set forth below.

EXAMPLE 1 A nylon thread, 45 denier, composed of 13 filaments, of 20-Z-twists per meter, was fed into the apparatus described above. The twisting tube turned at a speed of 287,000 turns per minute. The apparatus comprised two twist barriers, with twist barrier 1 set at a distance of cm. from the twisting tube and twist barrier 2' at a distance of 11 cm. from the twisting tube. The bobbin 4 which acted as a winding up mechanism was set at a distance of 16.5 cm. from the twisting tube. Twist barrier 2 was allowed to operate intermittently, at the rate of 72 times per minute. The thread was fed from the dolfing and wound up over the bobbin at a rate of 287 meters per minute.

The resulting twists are shown in FIG. 2, in which the length of the thread in meters is plotted on the abscissa, the number of turns per 5 cm. of the thread is plotted on ordinate and the straight line from the 0 point on the axis of the ordinate represents the zero points of the twist. It will readily be seen from FIG. 2 that the Z-twists alternated with S-twists, in spite of the fact that the direction of operation of the twisting tube was maintained constant.

The process of his invention may be readily applied to any type of raw materials, natural as well as synthetic, or blended materials. The process constitutes a substantial advance in an art, where it has been necessary to conduct the twisting step of filaments and threads as a separate operation, after spinning, and where is has been necessary, in order to impart to the thread or filament an alternating twist, to keep changing the direction of twist of the twisting device.

Although only one specific embodiment of this invention is described in detail, those skilled in the art will readily visualize that many variations are possible, without departing from the spirit of the invention, which is to be limited only by the scope of the appended claims.

What is claimed is:

1. A process for imparting an alternating twist to thread from natural, synthetic and blended material, which comprises feeding the thread at constant rate, and maintaining constant the rate of take-up of the thread, subjecting the thread to a twisting action at constant speed and constant direction, for a segment of length shorter than the distance between the site where the thread is fed and the site of application of the twisting action, alternately lengthening and shortening the thread segment which is subjected to the twisting action, whereby the thread segment being twisted alternates between a maximum and a minimum length, and twists accumulate in the shorter segment when the segment length is shortened, and twists of opposite direction are transferred to the thread when the segment length is lengthened, in the segment thereof after the site of application of the twisting action.

2. The process according to claim 1 wherein the thread travels along a path until it is wound onto a package, and said twisting action is applied at a point interposed thereon and the thread is subjected to at least one twist barrier action applied at a site between the site where the thread is fed and the site of application of the twisting action, whereby the thread segment which is subjected to the twisting action is of length shorter than the distance between the site of application of the twisting action and the site where the thread is fed.

3. The process according to claim 1 which is conducted continuously.

4. The process according to claim 1 wherein said alternately lengthening and shortening of the length of said thread segment which is subjected to the twisting action, is conducted gradually.

5. The process according to claim 1 wherein said alternately lengthening and shortening of the length of said thread segment which is subjected to the twisting action, is conducted abruptly.

6. The process according to claim 2 wherein said twist barrier action is shifted between two predetermined points along the path of travel of the thread before the site of application of the twisting action, whereby the thread segment which is subjected to the twisting action, is alternately lengthened and shortened.

7. The process according to claim 2 wherein two twist barrier actions are applied before the site of application of the twisting action at two predetermined points, the twist barrier action which is at the point nearer the site of application of the twisting action, being engaged intermittently.

8. The process according to claim 1 wherein twists of opposite direction are imparted to the thread segment which is being Wound after the site of application of the twisting action, after the thread segment has been twisted a number of times equal to in which a is the maximum length of thread segment being twisted, n is the number of rotation at constant direction imparted to the thread, per unit time, and v is the speed of the thread.

9. An apparatus for imparting alternating twist to thread from natural, synthetic and blended materials, which comprises feed means for the thread, means for winding the thread after the alternating twist is applied, whereby a package of wound thread is formed, twisting means for the thread at constant speed and constant direction interposed along the path between said feed means and the package of wound thread, at least one twist barrier means for the thread interposed along the path between said feed means and said twisting means, so as to reduce the thread segment between the feed means and the twisting means which is exposed to the action of the twisting means, and means for alternately lengthening and shortening the thread segment which is subjected to the twisting means whereby twists which accumulate in the shorter segment are transferred as twists of the opposite direction, to the thread segment between the twisting means and the wound package.

10. The apparatus according to claim 9 wherein said means for alternately lengthening and shortening the thread segment which is exposed to the twisting means, consist of said twist barrier means which are moved back and forth along the path of the thread, between two predetermined points before the site of the twisting means.

11. The apparatus according to claim 9 wherein said means for alternately lengthening and shortening the thread segment which is exposed to the twisting means, consist of two twist barrier means interposed along the path between said feed means and the twisting means, at predetermined points, and means: for intermittently engaging the twist barrier means which is nearer the twisting means.

12. The apparatus according to claim 9 wherein said twisting means is a twisting tube operating at constant rate.

13. The apparatus according to claim 9 wherein said twisting means is a fluid jet.

14. The thread made by the process of claim 1.

15. The thread made by the process of claim 3.

References Cited UNITED STATES PATENTS 2,952,116 9/1960 Burleson 57-34 XR 3,022,566 2/1962 Daniels et a1 57-140 XR 3,025,656 3/1962 Cook 57-64 XR 3,091,909 6/1963 Taylor et al. 57-34 3,105,349 10/1963 Palm et al. 57-34 3,129,485 4/1964 Shattuck 57-34 FRANK I. COHEN, Primary Examiner. W. H. SCHROEDER, Assistant Examiner.

US. Cl. X.R. 571l4, 157 

